MRI Evaluation of Indeterminate Pulmonary Nodules.

Abstract

Purpose: To evaluate MRI features for differentiating pulmonary hamartomas from other nodule pathologies, including carcinoid tumors and non-small cell lung cancer (NSCLC).

Materials and methods: This retrospective study analyzed chest MRIs of 48 patients with pulmonary nodules from 2017 to 2025. Patients had either pathologic diagnosis or stable follow-up confirming hamartoma. Two blinded radiologists reviewed images and recorded enhancement pattern (solid, rim, or speckled/mesh). The signal intensity index (SII) was calculated using chemical shift imaging.

Results: Hamartomas (n=19, 40%), carcinoids (n=17, 35%), and adenocarcinomas (n=9, 19%) were the most common diagnoses. Rim and speckled/mesh enhancement patterns were nearly exclusive to hamartomas (22% and 39% vs. 0% and 4%, respectively, P <0.001). An SII >10% showed 61% sensitivity and 100% specificity for hamartomas. Combining rim or speckled/mesh enhancement patterns and SII >10% yielded 79% sensitivity and 96.6% specificity for hamartomas.

Conclusions: Although chemical shift imaging is diagnostic for hamartomas, signal dropout is present in just over half of cases. Rim or speckled/mesh enhancement patterns are also highly suggestive. Combining these MRI features significantly improves diagnostic accuracy for pulmonary hamartomas, potentially reducing further follow-up or invasive procedures for indeterminate nodules.